Reconstructive Ultrasound Elastography to Determine the Shear Modulus of Prostate Cancer Tissue

In the field of medical diagnosis, there is a strong need to determine mechanical properties of biological tissue, which are of histological and pathological relevance. In order to obtain noninvasively quantitative mechanical properties of tissue, we propose in this work a new imaging modality which can be additionally used for the careful assessment of tumors in different soft tissues. This novel modality was named reconstructive ultrasound elastography, which is an inverse approach which can estimate the spatial distribution of the relative shear modulus of tissue from the measured axial deformation. First, during the solution of the mechanical forward problem the biological tissue was modeled as a linear isotropic incompressible elastic medium and a 2-D plane strain state model was used. Furthermore, to develop an inverse elastography reconstruction procedure, finite element simulations were performed for a number of biological tissue object models. The results obtained from finite element analysis were confirmed in the ultrasonic experiments on a set of tissue-like phantoms with known acoustical and mechanical properties. Finally, using numerical solution models and solving the inverse problem using two different methods we deduce the relative shear modulus of the sample. The used method is an iterative method for solving the inverse elasticity problem and is based on recasting the problem as a non-linear optimization problem.